Corrosion, dirt, and grime can build up on wheel rims over time, from exposure to weather and other elements during normal operation. Corrosion, in particular, often occurs on mating surfaces (e.g., the lip of the rim) which engage the bead of the tire, and the center of the rim, where the rim engages the hub. Corrosion in these areas is problematic, since it can prevent a good seal from being formed between the wheel and the tire, and prevent the wheel from mounting correctly on the hub.
The corrosion is often cleaned from these areas when tires are changed, since it is necessary to remove the tire from the wheel rim. To clean the rim, a grinder can be used to remove the corrosion from the affected areas. Current grinders use an enclosed shop vacuum to suck up metal filings as they are ground from the wheel. However, since the grinding process produces metal filings, which often include both aluminum and iron filings, there is a concern that the mixing of metal filings within the shop vacuum can produce a dielectric discharge and is a fire hazard.